Upon color development of a silver halide photographic material after imagewise exposure, an oxidized aromatic primary amine developing agent reacts with a dye-forming coupler (hereinafter referred to as a "coupler"), thereby forming a dye image.
Couplers which are used in recent color photographic materials must meet various requirements, such as high stability, high processing suitability, excellent color forming properties and an ability to produce a color image excellent in hue, as well as having fastness, low cost and high production suitability.
As cyan couplers, phenol-based and naphthol-based couplers have heretofore been used. In particular, 1-naphthol-based couplers have been widely used in color negative light-sensitive materials because the maximum absorption (.lambda.max) of the color-forming dye which they produce is in a longer wavelength side and the sub-absorption of the color-forming dye is decreased in the green-light region. Moreover, such couplers are excellent in color reproduction, are often excellent in color forming properties, are inexpensive and further are excellent in production suitability.
However, conventionally used phenol-based and naphthol-based couplers, particularly 2-alkylcarbamoyl-1-naphthol-based couplers, have the disadvantage that when processed with a fatigued or low oxidation power bleaching solution or bleach-fixing solution at the bleaching or bleach-fixing step of color development, they fail to produce a color image of sufficiently high color density. The reason for this is believed to be ascribable to reduction color fading of a cyan dye, for example, which is caused by ferric ions formed at the bleaching or bleach-fixing step. Furthermore, the above couplers also have the disadvantage that they produce a cyan image of low fastness.
The former disadvantage of the naphthol-based couplers as described above can be eliminated by changing the substituent of the carbamoyl group in the 2-position from an alkyl group to an aryl group, that is, by using 2-arylcarbamoyl-1-naphthol-based couplers (as described in U.S. Pat. No. 3,488,193, for example). However, it is impossible to eliminate the latter disadvantage even if the above couplers are used. Furthermore, from the viewpoint of image storage stability, it is now always desirable to use such couplers exclusively as the cyan couplers.
Of the naphthol-based couplers, 1-naphthol-based couplers having a specified substituent in the 5-position as described in European Patent No. 161,626 A2 are free of the disadvantages discussed above and are excellent in performance, but they suffer from the following disadvantages. That is, they are expensive to prepare them because many steps are needed in the preparation thereof. In addition, the degree of freedom in providing such couplers is small due to limitations in the preparation thereof. For reference, typical schemes for the preparation of 4-equivalent couplers are shown below. In these cases, as the starting materials, compounds described in Chemicals Guide, Kagaku Kogyo Jiho Co., Ltd., 1984-1985 ed., are used. ##STR2## 4-equivalent coupler wherein R represents a monovalent substituent, and R' represents an aliphatic or aromatic group. ##STR3## wherein R' represents an aliphatic or aromatic group.
It is apparent as illustrated above that the 5-position substituted type 1-naphthol-based couplers require more preparation steps than the usual 1-naphthol-based coupler and thus are of high preparation cost.
In addition, the 2-arylcarbamoyl-1-naphthol coupler and 5-position substituted type naphthol coupler have such disadvantages that they have a large sub-absorption in the shorter wavelength side, particularly in the blue light region, and this sub-absorption deteriorates the color reproduction of the light-sensitive material.